1. Field of the Invention
The present invention relates to a liquid crystal display apparatus and a method of driving the same, and, more particularly, to a liquid crystal display apparatus which displays color images using the birifringence of a liquid crystal.
2. Description of the Related Art
A liquid crystal display (LCD) panel for a color LCD apparatus generally has a liquid crystal (LC) cell, a pair of polarization plates sandwiching the LC cell, and a back light (illumination light source) located outside one of the polarization plates. The LC cell comprises a pair of transparent substrates with transparent electrodes formed on the opposing surfaces of the transparent substrates, and a liquid crystal sandwiched between the transparent substrates. One of the transparent substrates is provided with a color filter.
Conventional LCD apparatuses are driven by enabling or disabling the drive voltage to be applied between the opposing transparent electrodes to control the alignment state of the liquid crystal and causing the light from the back light to transmit or not to transmit through the LCD panel. When passing the color filter, the light from the back light is colored to the color of that color filter, thereby displaying a color image.
The light transmittance of the color filter is low, so that the conventional color LCD apparatus suffers a large light loss at the color filter, making the display darker.
In a reflection type LCD apparatus which employs a reflector in place of the back light, in particular, the incident light is absorbed by the color filter twice, before and after it is reflected at the reflector. This absorption darkens the display. It is therefore difficult to employ a color-filter using a color LCD panel in the reflection type LCD apparatus.
Under these circumstances, there has recent been developed an electrically controlled birifringence (ECB) type LCD apparatus which can display color images without using any color filter.
Since this ECB type LCD apparatus employs a different coloring method from that of the LCD apparatuses using a color filter, it cannot be driven directly by using an RGB signal which is used to drive an ordinary color LCD device using a color filter. Accordingly, the conventional ECB type LCD apparatus disregards color information and uses luminance information to provide the two-color (ON and OFF) display.
As another possible approach, the applied voltage may be altered in accordance with a display color which is specified by an RGB signal. This method, however, requires a process of temporarily developing a display image in a frame buffer and then changing the applied voltage according to the display color. This method therefore needs a relatively large-capacity frame buffer and involves complex data processing.